email with attachement gives image size 0

[admin]

Your camera uses digest auth mechanism which is not supported by socket.http library.
Use this code to get your snapshot:

Code:

local skthttp = require('socket.http')
local skturl = require('socket.url')
local ltn12 = require('ltn12')
local md5sum = require('encdec').md5

local hash = function(...)
  return md5sum(table.concat({...}, ':'))
end

local parse_header = function(header)
  local result = {}
  for key, value in (header .. ','):gmatch('(%w+)=(.-),') do
    if value:sub(1, 1) == '"' then -- strip quotes
      result[ key:lower() ] = value:sub(2, -2)
    else
      result[ key:lower() ] = value
    end
  end
  return result
end

local make_digest_header = function(headers)
  local digest = {}
  for _, header in ipairs(headers) do
    if not header.unquote then
      header[ 2 ] = '"' .. header[ 2 ] .. '"'
    end

    digest[ #digest + 1 ] = header[ 1 ] .. '=' .. header[ 2 ]
  end
  return 'Digest ' .. table.concat(digest, ', ')
end

local _request = function(req)
  if not req.url then
    return nil, 'missing url'
  end

  local url = skturl.parse(req.url)
  local user, password = url.user, url.password
  local sink = req.sink

  if not user or not password then
    return nil, 'missing credentials in url'
  end

  url.user, url.password, url.authority, url.userinfo = nil, nil, nil, nil
  req.url = skturl.build(url)
  local source
  if req.source then
    local chunks = {}
    local capture = function(chunk)
      if chunk then
        chunks[ #chunks + 1 ] = chunk
      end
      return chunk
    end
    local chunk_id = 0
    source = function()
      chunk_id = chunk_id + 1
      return chunks[ chunk_id ]
    end
    req.source = ltn12.source.chain(req.source, capture)
  end
  req.sink = nil
  local body, code, hdrs = skthttp.request(req)
  if code == 401 and hdrs['www-authenticate'] then
    local ht = parse_header(hdrs['www-authenticate'])
    if not ht.realm or not ht.nonce then
      return nil, 'missing realm/nonce from response'
    end
    local qop = ht.qop
    if qop and qop ~= 'auth' then
      return nil, 'unsupported qop ' .. tostring(qop)
    end
    if ht.algorithm and ht.algorithm:lower() ~= 'md5' then
      return nil, 'unsupported algo ' .. tostring(ht.algorithm)
    end
    local nc = '00000001'
    local cnonce = string.format('%08x', os.time())
    local uri = skturl.build({ path = url.path, query = url.query })
    local method = req.method or 'GET'
    local response = hash(
      hash(user, ht.realm, password),
      ht.nonce,
      nc,
      cnonce,
      'auth',
      hash(method, uri)
    )
    req.headers = req.headers or {}
    local auth = {
      { 'username', user },
      { 'realm', ht.realm },
      { 'nonce', ht.nonce },
      { 'uri', uri },
      { 'cnonce', cnonce },
      { 'nc', nc, unquote = true },
      { 'qop', 'auth' },
      { 'algorithm', 'MD5' },
      { 'response', response },
    }
    if ht.opaque then
      table.insert(auth, { 'opaque', ht.opaque })
    end
    req.headers.authorization = make_digest_header(auth)
    if not req.headers.cookie and hdrs['set-cookie'] then
      -- not really correct but enough for httpbin
      local cookie = (hdrs['set-cookie'] .. ';'):match('(.-=.-)[;,]')
      if cookie then
        req.headers.cookie = '$Version: 0; ' .. cookie .. ';'
      end
    end
    if req.source then
      req.source = source
    end
    req.sink = sink
    body, code, hdrs = skthttp.request(req)
  end

  return body, code, hdrs
end

local request = function(url)
  local t = type(url)
  if t == 'table' then
    return _request(table.clone(url))
  elseif t == 'string' then
    local req = {}
    local _, code, headers = _request({ url = url, sink = ltn12.sink.table(req) })
    return table.concat(req), code, headers
  end
end

url = 'http://admin:123456789@dnspruebacamara.myqnapcloud.com:5858/cgi-bin/snapshot.cgi?1&ts=123/snapshot.jpeg'
image, err, hdrs = request(url)